Fitting for formation of a fluid-conducting connection

ABSTRACT

1. Fitting for formation of a fluid-conducting connection 
     2. A fitting  5  for formation of a fluid-conducting connection on an opening in a wall  3  made of plastic of a container  1,  a tank in particular, for receiving a fluid, a hydraulic fluid in particular, having a connecting element  17  which is embedded on the edge of the opening in the plastic of the wall  3  of the container and which is provided with fastening means  15  accessible from the exterior of the container  1  by means of which a connection part  11  of the fitting  5  may be mounted on the connecting element  17.

The invention relates to a fitting for formation of a fluid-conductingconnection on an opening in the wall of a container of plastic, inparticular a tank for receiving a fluid, a hydraulic fluid inparticular.

Plastic tanks are widely used in hydraulic systems to contain hydraulicfluids. Because of the possibility of relatively simple configuration,low weight, and corrosion resistance, plastic tanks are extensively usedespecially in hydraulic systems of machines such as excavators, wheelloaders, and the like.

Such tanks are usually produced by the well-known rotomolding or blowmolding process, polyethylene or polyamide plastics, for example, beingused for larger containers such as tanks for hydraulic fluids.

The advantages of corrosion resistance, low weight, and ease of moldingare offset in the case of plastic tanks, however, by the disadvantagethat production of fluid-conducting connections on openings in theplastic wall of the container or tank occasions certain difficulties.Because of the physical properties of the plastic material, the dangerexists that deformations may occur in the area of the opening as aresult of sealing forces and temperature effects, deformations whichlead to leaking between plastic tanks and add-on elements even if costlysealing elements are employed.

On the basis of this state of the art the object of the invention is tomake available a fitting which permits operationally reliable long-termleak-free connection to an opening in a plastic container.

It is claimed for the invention that this object is attained by means ofa fitting possessing the characteristics specified in claim 1 in itsentirety.

The fitting claimed for the invention accordingly makes available,through the connecting element enclosing the opening in the containerand embedded in the plastic of the wall of the container, a reinforcingelement which is provided with fastening means for mounting of theconnecting element. The loads acting on the connection, such asfastening force, sealing force, dynamic (vibration) and thermal effects,do not act directly on the plastic material of the container wall butrather on the connecting element forming a reinforcing element.Embedding of a connecting element, which is made of an appropriatelyselected material with the operating loads taken into account,preferably metal or a duroplastic of high fatigue strength and thermalstability, affords reliable protection from deformation of the plasticmaterial of the container wall, so that a connection reliable inoperation and free of leaks is ensured.

The connecting element may to advantage be in the form of an insertedelement which is molded into the wall of the container in the moldingprocess in rotomolding of the plastic container.

When the opening in the container is round, the connecting elementpreferably is configured as a metal annular element the annular openingof which encloses and is aligned with the opening in the container. Theannular element may be of an aluminum alloy produced by injectionmolding, extrusion, or the like and preferably is configured so that ithas a level annular surface on its side associated with the outside ofthe container. It may be flush with the exterior of the wall of thecontainer surrounding the opening. As an alternative, the annularelement may be molded into the wall of the container so that the annularelement is slightly recessed in the container wall.

An especially close connection of annular element and the plastic wallof the container is obtained if the side of the annular element facingthe inside of the container has a plurality of pouch-like recesses. Ifthe annular element is molded as an inserted element in rotomolding ofthe container, the plastic material entering the pouch-like recessesforms a serration of the annular element with the container wall andprovides correspondingly good securing of the annular element againstloads.

The annular element may have bores for retaining screws as fasteningmeans for mounting, for example, a flange for fastening the respectiveclosing element.

By preference the bores are configured as blind-end bores with interiorthreading and are provided at regular angular distances on thecircumferential edge of the annular element.

The invention will be described in greater detail below with the aid ofthe exemplary embodiments illustrated in the drawing, in which

FIG. 1 presents a detached and a somewhat simplified perspective view indiagram form of a part of the upper side of the plastic tank having anexemplary embodiment of the fitting claimed for the invention forming aconnection for a so-called tank-top filter;

FIG. 2 presents a top view of the annular element of the exemplaryembodiment of the fitting claimed for the invention shown in FIG. 1;

FIGS. 3 and 4 present sections corresponding to section lines III-IIIand IV-IV in FIG. 2;

FIG. 5 presents a bottom view of the annular element shown in FIG. 2;

FIG. 6 presents a perspective diagonal view in the line of sight to thebottom of the annular element shown in FIG. 5, but drawn on a somewhatsmaller scale; and

FIG. 7 presents a detached and enlarged section of part of the upperside of a plastic tank with molded annular element recessed into thetank wall.

FIG. 1 illustrates a part of the upper side of a container in the formof a plastic tank 1 which is made of a plastic material suitable forlarger containers by the known rotomolding process (cf.Schaab/Stoeckhert, AKunststoff Maschinenführer@ [Plastic MachineOperator]), pages 561-564), a tank opening being formed on the upperside in the rotomolding process. There is on the opening in the plasticwall 3 a fitting designated as a whole as 5 for fluid-conducting,leak-free connection to a connecting element represented in theembodiment illustrated by the connecting head 7 of a tank-top filter thefilter element 9 of which projects through the opening to the interiorof the tank 1. The connecting head 7 has a fastening flange 11 which ismounted on the tank 1 by means of two retaining screws 13 only one ofwhich is visible in FIG. 1.

The retaining screws 13 extending through the fastening flange 11 arescrewed into internally threaded blind-end bores 15 which are providedon a connecting element configured as an annular element 17 additionaldetails of which are illustrated in FIGS. 2 to 6. The annular element17, in the present exemplary embodiment made of an aluminum alloy, ismolded as an inserted element in rotomolding of the tank 1 so that theround annular opening 19 forms the opening in the tank.

As is clearly to be seen in FIGS. 2 to 6, the annular element 17 has onits upper side, which is flush with the exterior of the plastic wall 3of the tank 1, a level annular surface 21 interrupted only by fourcylindrical pins 23 spaced at angular distances of 90°. These pinsproject a short distance above the annular surface 21 and are positionedon the circumferential edge so that they also project a certain distanceaxially above the circumferential edge of the annular element 17. Asshown in FIG. 1, only two of the four blind-end bores 15 on the annularelement 17 are used for engagement of retaining screws 13.

As is to be seen the most clearly in FIGS. 4 to 6, pouch-like recesses25 are made in the lower side of the annular element 17 all of which arenot identified by number in FIGS. 5 and 6; each recess 25 has a levelbottom 27 (see FIG. 4) and is of a depth which, as is shown the mostclearly in FIG. 4, amounts to more than three-fourths of the axiallymeasured thickness of the annular element 17. As is best seen in FIG. 5,the recesses 25 are positioned in sequence approximately in the centerbetween the unrecessed outer edge of the annular element and theunrecessed inner edge of the annular element. Except in the area of therecesses positioned in the area of the pins 23 of the blind-end bores15, the recesses 25 are more or less triangular in outline and arearranged in succession so that unrecessed areas of the annular element17 in the form of ribs 29 remain between adjacent recesses 25; the ribsextend between the annular opening 19 and the circumferential edge ofthe annular element 17, consecutive ribs 29 extending diagonally in anopposite direction relative to each other.

In order to effect sealing between annular element 17 and connectingelement the level annular surface 21 in the area between annular opening19 and the pins 23 on the annular element 17 may be provided as asealing surface adjoining an axial seal, for example. In the exampleillustrated in FIG. 1, sealing between annular element 17 and fasteningflange 11 of the connecting head 7 is effected by means of a radial seal(not shown) between fastening flange 11 and the inside of the annularopening 19 in the annular element 17.

As is shown by FIG. 7, the annular element 17 need not be molded intothe tank wall 3 so that the annular surface 21 is flush with the outsideof the wall 3. The annular element 17 may be embedded in the wall 3. Asillustrated by FIG. 7, the upper side of the pins 23 with the blind-endbores 15 may be flush with the outside of the wall 3. As FIG. 7 alsoshows, the outside of the annular element 17 is enclosed in its entiretyin the plastic material of the wall 3, this material also penetratingthe recesses 25.

1. A fitting (5) for formation of a fluid-conducting connection on an opening in a wall (3) made of plastic of a container (1), a tank in particular, for receiving a fluid, a hydraulic fluid in particular, having a connecting element (17) which is embedded on the edge of the opening in the plastic of the wall (3) of the container (1) and which is provided with fastening means (15) accessible from the exterior of the container (1) by means of which a connection part (11) of the fitting (5) may be mounted on the connecting element (17):
 2. The fitting as claimed in claim 1, wherein the connecting element (17) is in the form of an inserted element which is molded in rotomolding of the plastic container (1) into the wall (3) of the container (1) formed in the molding process.
 3. The fitting as claimed in claim 1, wherein the connecting element is configured as a metal annular element (17) the annular opening (19) of which encloses and is in alignment with the opening in the container (1).
 4. The fitting as claimed in claim 3, wherein the annular element (17) has a level annular surface (21) on the side associated with the exterior of the container.
 5. The fitting as claimed in claim 4, wherein the annular surface (21) is at least in approximation flush with the wall (3) of the container (1) surrounding the opening.
 6. The fitting as claimed in claim 3, wherein the side of the annular element (17) facing the interior of the container (1) has a plurality of pouch-like recesses (25).
 7. The fitting as claimed in claim 4, wherein a part of the level annular surface (21) of the annular element (17) is configured as a sealing surface, preferably for mounting of a sealing element, for formation of a seal opposite the connection part (11).
 8. The fitting as claimed in claim 3, wherein the annular element (17) has bores (15) for retaining screws (13) as fastening means for mounting a fastening flange of the connection part (11)
 9. The fitting as claimed in claim 8, wherein the bores are configured as blind-end bores (15) with internal threading and are provided at regular angular distances, distributed over the circumferential edge of the annular element (17).
 10. The fitting as claimed in claim 9, wherein the blind-end bores (15) are configured as cylindrical pins (23) projecting axially from the annular element (17).
 11. The fitting as claimed in claim 6, wherein the depth of the pouch-like recesses (25) constitutes at least three fourths of the axial thickness of the annular element (17).
 12. The fitting as claimed in claim 11, wherein at least a greater part of the pouch-like recesses (25) is in approximation triangular and wherein the recesses (25) on the annular element (17) are positioned in sequence such that non-recessed areas in the form of ribs (29) are formed between adjacent areas of the annular element (17), successive ribs (29) extending diagonally in the opposite direction relative to each other.
 13. The fitting as claimed in claim 12, wherein the area of the pouch-like recesses (25) is positioned centrally between a non-recessed outer edge of the annular element (17) and a non-recessed inner edge of the annular element (17). 